^urahara is an odd one though, so I'm sure he's perfectly visible to those without any reiatsu. In fact, have we EVER seen the guy actually abandon his gigai to fight? does he even have a gigai?
Kinda like the vizards/visoreds. at least shinji and Hyori could be seen by humans, yet you never see them abandon their corporeal bodies when they fought before( though you could always assume that everyone aside from shinji and hyori were always in shinigami mod)

"You have other hearts trapped within you as well, dont you?"
"You're that guy from last time! What are you talking about?!"
"The other Hearts within you."
"Hearts trapped within me....?"

If I remember correctly the gigai that Urahara, Tessai and the Vizards are in were only supposed to hide there reiatsu from SS, there not like the ones he gives to shinigami or Ichigo, so Tessai the Vizards and himself should all be able to use there shinigami powers.